In an undersea cable system, trunk and branch architectures provide a cost-effective way of connecting many landing stations to a single cable. Moreover, inherent to trunk and branch architectures are desirable features like security (very important when connecting many sovereign countries together) and high availability. (Security, as used herein, refers to the lack of direct access by a third-party node to the communications traffic between a first party node and second party node.)
An undersea cable system generally spans many countries, which may have diverse bandwidth needs so it is common for an undersea cable system to provide more than one level of bandwidth. For example, client signals may range from E1 (PDH (plesiochronous digital hierarchy)) level of transport (2 Mbps (millions of bits per second)) to synchronous transport module (STM)-16 (2.5 Gbps (Giga bits per second)), while the undersea transport infrastructure for these client signals may utilize higher rate signals such as STM-64 (10 Gbps and up). As such, various traffic grooming methods are used to increase utilization of the high rate undersea transport infrastructure.